RFR: JDK-8253879: Simplify redundant code in IndexBuilder

[Jonathan Gibbons]

Trivial cleanup to simplify `configuration.utils` to just `utils`, removing the redundant `configuration.`

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Commit messages:
 - JDK-8253879: Simplify redundant code in IndexBuilder

Changes: https://git.openjdk.java.net/jdk/pull/445/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=445&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8253879
  Stats: 7 lines in 1 file changed: 0 ins; 0 del; 7 mod
  Patch: https://git.openjdk.java.net/jdk/pull/445.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/445/head:pull/445

PR: https://git.openjdk.java.net/jdk/pull/445